Blind Bistatic Radar Parameter Estimation for AFDM Systems in Doubly-Dispersive Channels

TL;DR

This paper introduces a new blind radar parameter estimation method for AFDM systems in doubly-dispersive channels, enabling passive sensing without prior knowledge of transmitted signals, applicable to various waveforms in ISAC.

Contribution

The paper presents a novel covariance-based approach for blind bistatic radar parameter estimation that handles complex channel models without relying on signal knowledge or relaxation techniques.

Findings

Performance approaches ideal with more transmit frames

Method effectively estimates target ranges and velocities

Compatible with OFDM, OTFS, AFDM waveforms

Abstract

We propose a novel method for blind bistatic radar parameter estimation (RPE), which enables integrated sensing and communications (ISAC) by allowing passive (receive) base stations (BSs) to extract radar parameters (ranges and velocities of targets), without requiring knowledge of the information sent by an active (transmit) BS to its users. The contributed method is formulated with basis on the covariance of received signals, and under a generalized doubly-dispersive channel model compatible with most of the waveforms typically considered for ISAC, such as orthogonal frequency division multiplexing (OFDM), orthogonal time frequency space (OTFS) and affine frequency division multiplexing (AFDM). The original non-convex problem, which includes an $\ell_0$-norm regularization term in order to mitigate clutter, is solved not by relaxation to an $\ell_1$-norm, but by introducing an arbitrarily-tight approximation then relaxed via fractional programming (FP). Simulation results show that the performance of the proposed method approaches that of an ideal system with perfect knowledge of the transmit signal covariance with an increasing number of transmit frames.